1. Field of the Invention
This invention refers to an improved sliding chain-type ingot mold for a continuous casting plant.
2. Description of the Background
The production of billets and ingots by a continuous casting process formerly utilized stationary mold or shell-type elements in which the steel coming from the ladle and basket was introduced.
These plants have at in any case always suffered from considerable drawbacks, both from the viewpoint of productivity and of the difficulty of cooling the mold or shell-type elements.
It is in fact precisely the stationary structure of these mold or shell-type elements, being among other things of a limited longitudinal size, as well as the difficulties of maintaining contact between the solidified crust and the stationary structure, which allow only modest casting speeds, with a resulting slow and difficult heat dissipation from the mold or shell-type elements.
A solution was found in the production of trays capable of feeding several casting lines in parallel, all equipped with stationary mold or shell-type elements of the limited size mentioned above. However, even this solution involves some drawbacks, as any increase of the casting lines also causes an increase and a multiplication of the maintenance requirements and some heat dissipation problems.
Consequently, some plants have been developed which utilize a multiple number of mold or shell-type elements in motion, being firmly attached to two chains or crawler tracks arranged in a closed ring. These two chains arranged in a closed ring are over a straight portion of their path made to interface with each other, so as to generate a closed molding path to which the liquid metal coming from the trays can be directly fed.
Thanks to the lengthening of the longitudinal size of the closed mold, this system allows considerably boosting the casting speed, so as to attain the same productivity of three or four of the parallel lines described above. This also achieves the notable advantage of making it possible to operate directly in line with a subsequent rolling train or similar.
This type of continuous casting process, simply known as a sliding chain-type ingot mold, provides in particular, as mentioned, for two chains arranged in a closed ring, each carrying a multiple number of molding elements.
The molding elements can be made to interface with each other, so as to form a closed mold in the straight portion of the chain. In particular, in order to achieve this, a chain carries molding elements that are in one of their terminal portions capable of interlocking with the terminal portion of the molding elements carried by another chain. This produces a length of continuous cavity, formed in its interior by the interfacing and associated molds, in which the molten metal coming from the trays is cast.
Even this sliding chain-type ingot mold presents drawbacks and problems due to the deformations generated by the internal heat transmitted directly to the molten metal.
The deformations mainly cause a detachment of the two portions of the mold interfacing and associated with each other to form the cavity, with a resulting leakage of molten metal.
This also leads to a considerable reduction of the heat transmission, which overheats the copper structures designed to cool the interfacing molts, even up to the point of melting them.
Moreover, it is precisely because of these stresses that a deformation of the two interfacing molds occurs, causing slippages which lead to a rapid wastage of the same.